Map making method and templet for same



All@ 18, 1942 F` D. TERPENHIG I. Y 2,293,416

f MAP MAKING METHOD AND TEMPLET FOR SAME //v Vis/v Tof?` FRA/w( D.TER/25 /v//VG A T To APA/E vs.

@Y HAR/ens, /f/Ecf/ o5 Raf/ARRAS Aug. 18, 1942. F, D. 'rr-:RPENING MAPMAKING METHOD AND TEMPLET FOR SAME Filed June l2, 419140 2Sheets--Shee'tl 2 Patented Aug. 18, 1942 iliiiii STTS PTENT OFFICE2,293,416- ltiif'i? MAKNG PETHOD AND TEMPLET FOR SAME Frank l).Terpening, Los Angeles, Calif., assignor .y toFair-child, Polley &Eliel, Inc., Los. Angeles, Calif., a corporation of CaliforniaApplication Schei, 1940, Serial No.` 340,085`Y (Cl. y:i3-fl) 6 Claims.

My invention relates to the art of deriving maps from aerialphotographs, with special reference to such methods involving the use ofinterloclied templets and is directed specifically to a new and improvedtemplet procedure.

The basic mapping method of which the present invention is animprovement is set forth in the CollierPatent N o. 2,102,612 andtheEliel et al. Patent No. 2,180,406, which two patents may be taken aspart of the 4present disclosure.

In the procedure taught by the two patents, consecutive overlappingtemplets corresponding to consecutive overlapping photographs of terrainare assembled on a suitable working or map surface. Each of the templetshas a central aperture representing the reference center or opticalcenter of the correspondingV photograph and has slots disposed radiallythereof representing radial lines through reference points correspondingto clearly recognizable reference points appearing on the correspondingphotograph. The overlapping templets are interlocked by mechanical meanssuch as slidable posts passing through theintersecting slots, theinterlocking relationships being such that the positions of the posts,as determined automatically `by the intersecting slots, correspond tothe correct positions of the map points on a scale that is determined bythe adjustment of the templet assembly. When the templet assembly isadjusted to a desired scale, the map points located by mechanicaltriangulation in the above described manner are more often4 than. not atvariance with the original locations of the reference points as spacedon the original photographs. t then becomes desirable in most practicesof the basic procedure to enlarge or reduce the original photographstofcompensate for the discrepancies in the locations of the referencepoints as revealed by the automatic triangulation, the object being toachieve a revised set of photographs so scaled as to show the variousreference points at the precise locations determined by the templetassembly. In the usual procedure as described in theabove-mentionedpatents, a reference sheet is placed on the supportingsurface under the templet assembly and the locations of the various onthe reference sheet at the locationsyindicated by the templet assemblyand then the original photographs are checked against the spacings ofreference points on the reference paper to ascertain to precisely whatdegree the photographs should beenlarged or reduced for correction.

reference points are marked The general object of my invention is toreduce 5.5

u templets tothe desired reotion factors for the quired correctionfactors.

the .number of stepsv of the above described basic', procedure andtoreduce the possibilities for error in the procedure.` Myrinventionrelatesprif marily to the steps following the 4assembly of the scale, i.e., the rsteps. that` are taken to achieve a final set of photographsatV such scale. It is mypurpose4 to shorten this latter portion of theprocedureand to increase accuracy by a newmethod of. deriving thecorvarious photographs. Characterizing my invention is the concept thatscales 4may be imprinted or otherwiseprovided on the individual templetsfor visual .comparative measurements leading directly tothe re-v One ofmy specific objects in this aspect of theinvention isto provide a simpleand eicientscale for the suggested purpose. Another specic object .in4mind is ,to provide a means. for slotting and marking a teme `plet tofacilitate the use of the imprintedscale.

A further object of the invention is, to expe,- dite and simplify themap making procedure by providing a combination of ratio camera andscaledtemplets in which the. camera has `a scale functionally related tothe templet scales. A

feature ofthe invention in this aspect is the con-v A cept of usinglogarithmic scales on both the tem-V plet and ratio `camera for reducingthe required correction computation to simple, substraction of visuallyascertained scale values.

The above and-other of my invention will be apparent in the following`detailed description, consideredwith the accom. panying drawings.

In the drawingswhich are to be taken as ll.- lustrative only: v

Fig. l is a view of an aerial photographtaken by an aerial mappingcamera Fig. 2 shows one of my novel templets inthey process ofpreparation;

Fig. 3 shows the templet `after it has been punched and slotted;

Fig. 4 is a partly sectioned elevational view showing 1a device forslotting the templet witha somewhat reduced sc ale ofy a templetassembly on a supporting surface;

lig. 8 is a perspective View ofone of the cori-- objects and advantagesjoining posts employed to interlock the templets in the assembly of Fig.'7;

Fig. 9 is a plan View of three of the interlocked templets on a largerscale;

Fig. 10 is a fragmentary View on a still larger scale taken as indicatedby the line l-HJ of Fig. 9;

Fig. 1l is a fragmentary plan View corresponding to Fig. l0; and

Fig. l2 is a side elevation of a camera device for reproducing thephotographs at corrected scales.

In the usual map making procedure by aerial methods, an airplanecarrying a camerais flown back and forth along adjacent and parallellines over terrain to be mapped and consecutive photographs of theterrain are taken-in such sequence that one photograph overlaps thepreceding photograph by more ably about 60%. The camera is provided withmeans for indicating the center point of each photograph as a referencecenter for subsequent triangulation. severally. outlying clearlyrecognizable points on each photograph are selected for the purpose ofcoordinating overlapping photographs by triangulation. If all of thephotographs are to the same scale and are disposed in correctoverlapping relation with lines radiating from the reference centers ofthe photographsto the selected outlying reference points, each referencepoint will be common to a plurality Vof photographs and will lie atV theintersection of the corresponding radial lines of the overlappingphotographs. In practice the initial photographs arenever uniform inscale because the Vmost skillful pilot cannot maintain a desiredelevation relative to varying terrainy One, purpose of usinginterlocking templets to represent the photographs is to ascertainvariationsjin scale of the photographs so that reproductions of thephotographs may be made to uniform scale.

An understanding of the present invention may be .approachedadvantageously by first reviewing the standard procedure that hasheretofore prevailed.` Part of the present drawings may be of assistancein this review if circular scales appearing on the templets aredisregarded.

Fig. l shows a typical photograph 2li on which the reference center 2iis indicated, this center point being hereinafter termed the referencecenter. A number of selected outlying points that are clearlyrecognizable in the photographic image are indicated thereon by dots 22.The drawings show corresponding lines 23 from the reference center 2l tothe dots 22 to indicate the radial dispositions of the dots, but suchlines are usually not actually drawn on the photographs.

Fig.V 2 shows at an early stage of development a templet 25 representingthe photograph 2B, the templet being marked with the reference center 2land the various outlying reference points 22 of the photograph. Thevarious points may loe plotted on the templet 25 by the simple procedureof placing the photograph 2@ over the templet and piercing both thephotograph and templet with a needle-like instrument at the indicatedpoints. To make the various points on the templet conspicuous andthereby reduce the likelihood of error, I prefer to mark circles 2Saround each of the outlying reference points 22.

After the templet is marked in the manner described, a hole 2'! ispunchedconcentric with the reference center 2i, as shown in Fig. 3, and

than 50%, prefersome suitable device having centering means cooperativewith the hole 2 is employed to cut radial slots 23 in the templet toindicate the locations and the radial dispositions of the variousoutlyiing reference points 22. The drawings show in Figs. 2 and 3 thepreviously mentioned radial lines 23 to emphasize the fact that theslots are in accurate radial disposition, but in practice such radiatinglines are not required.

'Ihe next step in the old procedure is to assemble the slots inoverlapping disposition on a suitable work surface with the templetsinterlocked into a coordinated assembly by a number of templet postssuch as the templet post 3i! in Fig. 8. Such a templet post has anupright cylindrical stem :il of a diameter to slidingly flt the templetslots and has a wide base portion 32 on which the post may slide over asupporting surface. The post has an axial bore 33 through which theposition of the post may be marked on the underlying surface or throughwhich an anchoring pin 35 may be inserted, as shown in Fig. l0.

Fig. 7 shows a number of overlapping templets 25 interlocked by varioustemplet posts Sil that engage the various central holes 2l and radialslots 25S of the templets. In Fig. '7 the assembly rests upon what maybe termed a reference sheet or mapping sheet 35 which is spread on awork table Si. Within rather liberal limits permitted by the slots 28the assembly of templets may be expanded and contracted in a coordinatedmanner, the relative spacing of the posts Sii increasing and decreasingaccordingly and the posts causing each of the templets to move formaintenance of the correct position of the templet relative to theassembly as a whole. In the particular templet assembly shown in Fig. 7,three of the pins 35 anchor three of the templet posts Si! atpredetermined points on the reference sheet 3b and thereby x thelongitudinal extension of the templet assembly in accord with the scalerepresented by the three predetermined points.

The manner in which the templets interlock is best shown by the threetemplets lil, ft2, and ES in Figs. 9, 10, and ll. Each of the threetemplets Lli, i2, and i3 is shown with the usual center hole 21 andradial slots 28 so that the templets may beV interlocked by employingthe required number of templet posts B. It will be obvious in Fig. 9that the uppermost templet il has a marginal portion l5 that overlies acentral portion of the intermediate templet li? and also overlies amarginal portion of the undermost templet 33. In an assembly of numeroustemplets, each of the posts, with a few exceptions along the margin ofthe assembly, will eX- tend through at least three of the templets.Figs. 9, 10, and 11 show a post 39a extending through a slot do in theuppermost templet iii, a slot 41 in the intermediate templet 42, and aslot i3 in the lowermost templet 43.

The longitudinal center of the uppermost slot 45 is the location of thecorresponding reference point 22 that was plotted on the templet priorto the slot-cutting operation. It is to be noted, however, as best shownin Fig. 1l, that the post 30a is shifted outwardly from the longitudinalcenter of the slot. The final position of the post 3M may be called thetriangular vdetermination or the corrected location for the originalreference point for which the slot is cut. The outward shift of the post39a as caused by cam 'action on the part of thet'hree associated slotsin the process of 'assembling and adjustingthe templet assemblyindicates that the original photograph on which the templet is basedmust be enlarged to conform with the scale of gthe -templet assembly.Such enlargement of a,photo graph, of course, in effect causes all ofthe ou*- lying reference points to shift radially outward. Fig. l, forexample, indicates in, dotted linesshow the photograph 2u may beenlarged tocause the reference points in effect to move outward topositions 22a.

In the older practice under the two previously mentionedpatents, theprocedure afterthe templets are properly assembled is as follows. Pinssuch as the anchoring pins 35 are inserted through the axial bores 33 ofthe various templet posts 39 to prick the underlying reference sheet,thereby marking on the reference sheet vthe correct locations of all ofthe reference points 22. Legends or symbols are then marked onthereference sheet to identify the various reference points, whichreference points of course include the reference centers of the varioustempiets. The templet assembly is then removed from the reference sheetand comparison is made between each of the photographs represented bythe templets and the locations of the corresponding points on thereference sheet. The comparison is made by measuring on the referencesheet the distance between a reference center and an associated outlyingreference point and then incasuring on thecorresponding photograph thecorresponding spacing between the redrence center and the outlyingreference point. The spacing derived from the reference sheet is thendivided by the spacing taken from the original photograph to arrive at aratio or correction factor for guidance in reproduction of thephotograph by enlargement or reduction to the required scale.

The improvement represented by the present invention is primarily in theprovision ofa circular scale for each of the templets and in the savingof time and the increasing of accuracy achieved by the addition of the..templet scale. Since the purpose of the scale is to facilitate thecomparison of distances from the templet center, the scale may expressany units of measurement, for example, inches or centimeters. A featureof my invention, however, is that outstanding advantages may be had byusinga scale to indicate the logarithme of spacingvalues, the scale, forexample, indicating the logarithins of distances in inches. Sincemeasurements along only one radial line of the many available on atemplet are necessary to reach a correctionfactor for the photograph,the scale may be confined to substantially one radial direction, but Iprefer to use full circles for the graduations to produce a concentricscale that maybe employed to ascertain radial measurements onthe yfaceof thetemplets in any radial direction.

In the particular arrangement suggested by the drawings, each of thetemplets is imprinted with a circular scale generally designated t. Theinnermost circle 5! (Fig. 9) has a radius of exactly one inch and has ascale value of zero since `the logarithm of l is Zero. The fth circle 52from the ce. ter having the scale value 1 is at approximately an inchand a quarter from the center, since the log 0.1600 will representapproximately 1.259 inches.

Referring to Fig. 1l, it is apparent that since the radial slot 23 ispunched symmetrical to the preferred practice ofv my inventiomlprovide-index means associated with eah of the radial slots 28 toindicate at a glance the radial distance of the slot center formeasurment on the circular scale 513.1 Thus, as shown in Fig. 11, I mayimpress or imprint index marks 53 on, the templet at the sides of theslots to indicate the locations of the centersof the slots.

To providethe index marks 53 for the slots 28 without adding a step tothe usual procedure for ac marking and punching the templets, Icontemplate using a special slot-cutting device constructed as indicatedby Figs. 4, 5, and 6. The slot-cutting device or templetV punch includesa base 55 providing a work-support surface 55 and equipped with asuitable pin or post 5l" for entering with fairly close fittheaforementioned central reference hole 27 in a templet 25. The cuttingmeans proper includes a die opening 58 in the base 55 and acomplementary punch mem- Iber GE) that is slidingly retained by guidewalls Si formed in an arm 62 that is mounted on the base to overhangAthe die opening. The cutting i movements of the punch member 6E? aregoverned by an operating handle 63 that is connected to the punch member6B by a suitable link E54.

Since it is necessary to provide for varying at will the distance of theindividual slots from the templet reference center 2 l, which referencecenter is represented by the central hole 2, it is `ncessary to providefor relative movement between the slot-cutting means andthe-post 5?. Inthe particular construction shown in thedrawings, the requiredadjustability is achieved simply by mounting the post 57 in a movablemanner on the base 55. For example, the

vided with a base ange 55 and slidingly mounted in a complementary guideslot 6ft, the slot having the cross-sectional configuration of aninverted T. It will be noted by an inspection of Fig. 5 that thelongitudinal axis of the cutting pattern, in other words the long axisof the die opening 58 or the long axis of the punch member 6I) in crosssection, is in radial alignment tothe axis of the post 51, and that thelongitudinal axis of the guide slot 65 coincides with such radialalignment. Means to insure cutting the radial slots accuratelysymmetrical to the various outlying reference points 22 of the templetsmay comprise a needle-like member Si extending downwardly from member60.

post may be pro- The slot-cutting device described tol this pointv isone form of slotting device that has heretofore been commonly used inthe practice methods disclosed by the patents. My contribution tofacilitate the practice of the present invention consists of addingmeans to the slot-cutting device to apply index means such as the indexmarks 53 to the templets simultaneously with the punching of the templetslots. For example, I may add die members or suitable lateralprojections ber 69 to impress the material of the templet adjacent theslots when the slots are out. The lateral projections 'lil are spacedabove the cutthe cutting face of the punchof the i aforementioned two'IB to the punch mem-v 4 ting face of the punch member 60 so that afterthe punch member shears away the material of a templet to form a radialslot, continued downward movement of the punch member causes suitablysharp edges 1| of the projections to compress the material of thetemplet against the work-support 56 of the base 55, thereby creasing thetemplet to form the index marks 53.

Turning again to Fig. l1 for illustration of the new procedure, it isapparent that the operator may note at a glance the two values necessaryfor computing the correction factor for the corresponding photograph.The operator notes the log 0.802 for the position of the axis of thepost 30a and the log 0.762 for the index marks 53. subtracting log 0.762from log 0.802 the operator obtains the log 0.040 representing the ratiobetween the `two radial distances which is the correction factor for thecorresponding photograph. Expressed in inches the actual radial distanceof the post 30a is 6.339 and the actual radial distance of the indexmark 53 is 5.781. While these measurements of inches are expressed inthousands because they are derived from the logs 0.802 and 0.762 it isapparent, of course, that since the log values are based on mereinspection and visual comparison with the log scale 50, accuracy to thethousandth of an inch is not actually obtainable. The values derived bythe described visual procedure are, however, su'iciently close tocorrect values to result in map work of the required degree of accuracy.The log 0.040 indicates that the correction factor is 1.096, and that aphotograph'to the correct scale may be obtained by enlarging thecorresponding original photograph to increase its dimensions by 096%.

The actual number expressing the correction factor may be derived fromthe difference in the log readings by reference to a table oflogarithrns so that a ratio camera or enlarging printer with aconventional ratio scale may be employed to produce the correctedphotograph. A feature of the preferred practice of my invention,however, is the further conception that any necessity for translatinglog values into corresponding numbers may be entirely avoided byemploying a ratio camera or enlarging printer with a ratio scaleexpressed in logarithme.

Fig. 12 shows a ratio camera or printer comprising a base 15, an easel16 movably mounted on the base, and an adjustable projector generallydesignated 11. Included in the adjustable projector is a film holder 18,a lens 19 and a bellows 80 extending from the film holder to the lens. Anegative film being in the film holder 18, light from a suitable source(not shown) at the rear of the lm passes through the lens 19 to projectan image of the film pattern on the easel 16, the ratio of the imagedimensions to the dimensions of the film pattern being determined by theadjustment of the easel and the projector. The scale for the printer isin fact two scales with indentical readings, a scale 8l for adjustmentof the easel 16 and a scale 82 for adjustment of the projector 11. Bothscales are in logarithms of correction factors, the zero point for eachscale representing the adjustment of the printer that corresponds to thesize of the original aerial photographs.

In recapitulation, the advantages of the practice afforded by myinvention may be emphasized by comparing the steps in the new procedurewith the steps followed in the older procedure of the previouslymentioned patents.

2. Plotting the reference centers of the photol graphs and the selectedmap points or outlying reference points on a series of templetscorresponding to the series of the photographs.

3. Punching radial slots in the templets symmetrical to each of theselected reference points.

4. Interlocking the series of related templets on a work surface andadjusting the templets to a required scale by anchoring selected postsat predetermined points on the map surface.

5. Plotting and identifying the positions of the interlocking posts ofthe templet assembly on a reference sheet under the map assembly.

6. Measuring on the reference sheet the distance from the referencecenter of each templet to a selected one of the outlying referencepoints of the templet area on the reference sheet.

7. Measuring on each of the original photographs the correspondingdistance from the reference center to the selected outlying referencepoint.

8. For each photograph dividing the radial distance derived from thereference sheet by the corresponding radial distance obtained bymeasurement on the photograph to obtain a correction factor.

9. For each original photograph setting a ratio camera or enlargingprinter to the required correction factor and making a new print of the'photograph.

The steps of the present method are:

l. Marking selected map points on the series of original photographs.

2. Plotting the reference centers of the photographs and the selectedmap points or outlying reference points on a series of templetscorresponding to the series of the photographs.

3. Punching radial slots in the templets symmetrical to each of theselected reference points, and simultaneously marking indices on thetemplletts to indicate the longitudinal centers of the s o 4.Interlocking the series of related templets on a work surface andadjusting the templets to a required scale by anchoring selected postsat predetermined points on the map surface.

5. Noting by inspection of the templet assembly the value on the logscale of each templet indicated by the position of a selected templetpost representing an outlying reference point.

6. Noting by inspection the value on the log scale of each templetindicated by the corresponding index marks 53 at the slot through whichthe selected templet post extends.

'7. subtracting the logarithm of step 6 from the logarithm of step 5 foreach templet to ascertain the logarithm of the correction factor for thecorresponding photograph.

8. For each original photograph, setting the ratio camera or enlargingprinter to the logarithm derived in step 1 and making a new print of thephotograph.

The fact that the new method has eight steps instead of the nine stepsof the old method is only one of the advantages apparent in the abovecomparison. One of the additional advantages is that the use of areference sheet under the map assembly for arriving at the correctionfactors is eliminated. Another advantage is that the values are obtainedwithout the manual application of any ruling devices whatsoever. Afurther consideration is that in carrying out the old pro- 'cedure, care'must' be taken to pair the measure- "ments on the reference sheet withthe correspond- 'fing' Vmeasurements "on the photographs,` whereas "inthe new procedure' the two values that must be pairedfor comparison areread consecutively in the same radial direction on the same templet. Astill further'advantage is that the computations for each photograph arereduced tomerely the subtraction of one logA from another. It isapparent that the procedure is inherently accurate Uand involves fewerchances for error than the older procedure.

The preferred form oftemplet and the preferred procedure in the practiceof my invention described herein, for the purpose of disclosure and toillustrate the principles involved, will suggest to those skilled in theart various changes and modifications both in the templet and in theprocedure; it is to be understood that I reserve the right to all suchchanges and modiiications that properly come within the scope of myappended claims.

I claim as my invention:

1. A method of making maps from aerial photographs by employing templetseach corresponding to one of said photographs, each of said templetsbeing provided with a central hole the center of which corresponds to acentral reference point on the corresponding photograph and a pluralityof angularly disposed slots each said slots being laterally symmetricalwith a radial line through said center and a point corresponding toanother point on the corresponding photograph, which method comprises:malnfng index marks on the upper' surface of each the distance on thecorresponding photograph between two reference points; interlocking saidtemplets in overlapping relation by interlocking members passing throughsaid holes and said slots; determining on the upper surface of each ofsaid templets the distance between the centers of the intcrlockinUmembers corresponding to said two points; and comparing the last nameddistance with said indicated distance to obtain a correction factor forthe corresponding phcto- I graph.

2. A method of making maps from aerial photographs by employing templetseach corresponding to one of said photographs and each having a centralreference point representing a central reference point of thecorresponding photograph, which method comprises: marking on each ofsaid templets a plurality of outlying reference points corresponding tooutlying points on the corresponding photograph; cutting slots in saidtemplet :g

radially of said central reference point and laterally symmetrical tosaid outlying reference points, thereby removing the templet material onwhich said outlying reference points are marked; making an index mark onthe upper surface of said templet adjacent at least one of said slots toindicate the radial distance of the corresponding outlying referencepoint on the material removed in forming the slot; providing a scale ofradial distances on the upper surface of said templet along the slotcorresponding to said index mark; and comparing the positions withreference to said scale of said index mark and the interlocking memberin the corresponding slot to obtain the correction factor for thecorresponding photograph.

3. A method of making maps from aerial photographs by employing templetscach corresponding to one of said photographs and each having a centralreference point representing a central reftemplet indicating thereonpoints, thereby removing the templet -whichsaid outlying referencepoints 'said templet adjacent Vatleast one to indicate the radialdistance of the erence point of the corresponding photograph,

which method comprises: marking/on each of said templets a pluralityofoutlying reference points corresponding tooutlyingpoints on thecorresponding photograph; cutting slots in said templet radially of saidvcentral reference point and laterally symmetrical of said outlyingreference material on are marked; making an index mark on theupper'surface of of said slots corresponding outlying reference point onthe material re- `'movedi-n formingthe slot; providing a logarithmicscale offradialidistances on the upper surface of saidtemplet along theslot corresponding to said index mark; deriving by inspection of eachinterlocked templet the logarithms on said scale represented by thepositions of the index mark and of the interlocking member; andsubtracting one of said logarithms from the other to obtain thelogarithm of the correction factor for the corresponding photograph.

4. A method of making maps from aerial photographs by employing templetseach corresponding to one of said photographs, each of said templetsbeing provided with a central hole the center of which corresponds to acentral reference point on the corresponding photograph, which methodcomprises: cutting a plurality of angularly disposed slots eachlaterally symmetrical with a radial line through said center and a pointcorresponding to another reference point on the correspondingphotograph; making an index mark on the upper surface of each templetindicating thereon the distance on the corresponding photograph betweensaid central and said other reference point; interlocking said empletsin overlapping relation by interlocking members passing through saidholes and slots; determining on the upper surface of each of saidtemplets the distance between the center of the central interlockingmember and the center of an interlocking member corresponding to saidother reference point; and comparing the last named distance and theindicated distance to obtain a correction factor for the correspondingphotograph.

5. A method of making maps from aerial photographs by employing templetseach corresponding to one of said photographs, which method comprises:cutting a plurality of angularly disposed slots in said templet, each ofsaid slots being laterally symmetrical with a radial line through acentral point corresponding to a central reference point on thecorresponding photograph and a point corresponding to another referencepoint on the corresponding photograph; providing a scale on the uppersurface of said templet extending from said point corresponding to saidcentral reference point outwardly adjacent at least one of said slots;making an index mark on the upper surface of each templet indicating onsaid scale the distance on the corresponding photograph between saidcentral and said other reference point; interlocking said templets byinterlocking members passing through said slots; determining from saidscale on each of said templets the distance between the central pointcorresponding to said central reference point and the center of aninterlocking member corresponding to said other reference point; andcomparing the last named distance and the indicated distance to obtainthe correction factor for the corresponding photograph.

6. A method of making maps from aerial photographs by employingtemplets, each corresponding to one of said photographs, each of saidtemplets being provided with a circular logarithmic scale the center ofwhich corresponds to a central reference point on the correspondingphotograph, which method comprises: cutting a plurality of angularlydisposed slots each laterally symmetrical with a radial line throughsaid center and a point corresponding to another reference point on thecorresponding photograph; making an index mark on the upper surface ofeach templet indicating on said scale the logarithm of the distance onthe corresponding photograph between Vsaid central and said otherreference point; interlocking said templets in overlapping relation byinterlocking members passing through said slots, determining on theupper surface of each-of said templets from said scale the logarithm ofthe distance between the center of said scale and the center of aninterlocking member corresponding to said other reference point;comparing said logarithms to obtain the logarithm of a correction factorfor the corresponding photograph; and reproducing the correspondingphotograph on an enlarged or reduced scale as indicated by saidlogarithm of said correction factor.

FRANK D. TERPENING.

D CERTIFICATE oF- CORRECTION. Patent No. 2.295JL16 T l August i8, 19m.

' FRANK D. TERTENING.

It is hereby certifiedlihe't error appears in the printed specificationof theebove numbered patent requiring correction asi-follows: PageLeecond column, line 1,9, after "mein-s"v insert --and method; .line 29,for ":subs:trxavction'l read -lfsiibt'ractin--t page 2, secondcolumnyline 5h., for *spacing* read -spacng`s'; page 5, secondco1umn,vlne )4.0, for vnnces# gary read necesery-tkl page L, firstcolumn, line 6 5', for "indentical read -identca1-; and chei-l the 'saidLetters Patent should be read with i this correction l'therein 'that thesame may conform to the record of the case in t'he Patent Office.

sigred and' sealed this 29thv day of september, A. D. 19M.

Henry Ven Arsdale, (Seal) 'Acting Commissioner of Ptente.

